Allows reading TMY data from a Path or file-like object (#2544)

* Allows reading TMY data from a Path or file-like object

* Reverts "filename" parameter rename for consistency

* Fixes linter issue in tests

* Updates "What's New" docs for change

* Adding a couple of more assertions for TMY3 parsing test

Author: jerluc

docs/sphinx/source/whatsnew/v0.13.1.rst

@@ -29,6 +29,8 @@ Enhancements
   (:pull:`2500`)
 * :py:func:`pvlib.spectrum.spectral_factor_firstsolar` no longer emits warnings
   when airmass and precipitable water values fall out of range. (:pull:`2512`)
+* Allows reading TMY data from a Path or file-like object in :py:func:`~pvlib.iotools.read_tmy3`.
+  (:pull:`2544`, :ghuser:`jerluc`)
 
 Documentation
 ~~~~~~~~~~~~~

pvlib/iotools/tmy.py

@@ -4,6 +4,8 @@
 import re
 import pandas as pd
 
+from pvlib.tools import _file_context_manager
+
 # Dictionary mapping TMY3 names to pvlib names
 VARIABLE_MAP = {
     'GHI (W/m^2)': 'ghi',
@@ -35,7 +37,7 @@ def read_tmy3(filename, coerce_year=None, map_variables=True, encoding=None):
 
     Parameters
     ----------
-    filename : str
+    filename : str, Path, or file-like object
         A relative file path or absolute file path.
     coerce_year : int, optional
         If supplied, the year of the index will be set to ``coerce_year``, except
@@ -186,7 +188,7 @@ def read_tmy3(filename, coerce_year=None, map_variables=True, encoding=None):
     """  # noqa: E501
     head = ['USAF', 'Name', 'State', 'TZ', 'latitude', 'longitude', 'altitude']
 
-    with open(str(filename), 'r', encoding=encoding) as fbuf:
+    with _file_context_manager(filename, mode="r", encoding=encoding) as fbuf:
         # header information on the 1st line (0 indexing)
         firstline = fbuf.readline()
         # use pandas to read the csv file buffer

pvlib/tools.py

@@ -562,7 +562,7 @@ def normalize_max2one(a):
     return res
 
 
-def _file_context_manager(filename_or_object, mode='r'):
+def _file_context_manager(filename_or_object, mode='r', encoding=None):
     """
     Open a filename/path for reading, or pass a file-like object
     through unchanged.
@@ -584,5 +584,5 @@ def _file_context_manager(filename_or_object, mode='r'):
         context = contextlib.nullcontext(filename_or_object)
     else:
         # otherwise, assume a filename or path
-        context = open(str(filename_or_object), mode=mode)
+        context = open(str(filename_or_object), mode=mode, encoding=encoding)
     return context

tests/iotools/test_tmy.py

@@ -19,6 +19,13 @@ def test_read_tmy3():
     tmy.read_tmy3(TMY3_TESTFILE, map_variables=False)
 
 
+def test_read_tmy3_buffer():
+    with open(TMY3_TESTFILE) as f:
+        data, _ = tmy.read_tmy3(f, map_variables=False)
+        assert 'GHI source' in data.columns
+        assert len(data) == 8760
+
+
 def test_read_tmy3_norecolumn():
     data, _ = tmy.read_tmy3(TMY3_TESTFILE, map_variables=False)
     assert 'GHI source' in data.columns